1. Field of the Invention
This invention relates to a method for removing high molecular weight low melting point hydrocarbon vapors from an offgas stream produced during liquefaction of a waste plastic material, and more particularly for utilizing the offgas vapor stream as a heater fuel for the liquefaction process.
2. Description of the Prior Art
Diminishing natural resources as well as economic considerations have led to the increasing use of organic feedstocks from impure sources, such as scrap or waste plastic materials.
Waste or scrap plastic materials often comprise at least one solid carbonaceous thermoplastic and/or thermosetting material which may or may not contain associated inorganic matter, such as fillers and reinforcement material. Such materials may be derived from obsolete equipment, household containers, packaging, industrial sources, recycling centers and discarded automobiles. Scrap plastic comprises solid organic polymers derived from sheets, films, extruded shapes, moldings, reinforced plastics, laminates and foamed plastics. The mixture of scrap plastics varies with the source and with the presence of non-combustible inorganic matter incorporated in the plastic as fillers, catalysts, pigments and reinforcing agents.
It is desirable to convert particulate scrap plastic into a liquid hydrocarbonaceous feedstock for a partial oxidation reaction to produce gas mixtures of hydrogen and carbon monoxide, referred to as synthesis gas, or simply "syngas." Syngas can be used to make other useful organic compounds or as a fuel to produce power.
The partial oxidation reaction can be conducted in a free-flow unpacked noncatalytic quench gasifier. The reaction temperature varies about 1800.degree. F. to about 3000.degree. F. and the reaction pressure is about 1 to about 100 atmospheres, preferably about 30 to about 80 atmospheres.